The present invention relates to scroll type fluid machinery, which can be used as compressors, vacuum pumps, expander machines, etc.
Double-scroll fluid machinery has got people's attentions due to its many advantages such as thrust force canceling. The technology of Double-Scroll linked by a Plurality of Orbiting units (DSPO) revealed in US patent U.S. Pat. No. 6,988,876 has two volume changing mechanisms, each of which comprises its respective orbiting scroll and stationary scroll. The two stationary scrolls are connected with a housing. Orbiting units are located between the two volume changing mechanisms. Each orbiting unit comprises a rotating member that is rotatably supported on the housing, and a thrust-canceling shaft that is eccentrically and rotatably supported in the rotating member. The thrust-canceling shaft connects the two orbiting scrolls with its two ends to form a frame structure. The orbiting scrolls orbit with respect to the matching stationary scrolls when the rotating members are driven, and thus the continuous changes of the volumes are realized.
It has been revealed in Chinese Patent Publication CN1963205A that DSPO can easily realize internal fluid injection cooling (especially water injection), because the volume changing mechanisms and the orbiting units are separated by the decompression chambers, and the bearings are not installed directly on the orbiting scrolls.
Due to the engagement between DSPO's orbiting scrolls and the respective stationary scrolls, the two orbiting scrolls are required to connect with the thrust-canceling shaft accurately in both radial and axial directions. However, it is not practical to have through holes on the end plates of the orbiting scrolls for installing and tightening the thrust-canceling shaft, since one side of the end plate is a working surface of the compressing chamber. Therefore, the installation and adjustment of the thrust-canceling shaft into the orbiting scrolls are pretty tough.
DSPO's orbiting units have two bearing groups, the thrust-canceling shaft supporting bearing group, and the rotating member supporting group. The former is installed inside with a very small space, though it withstands a larger load. The current DSPO technology still has issues in resolving the heat dissipating, and the adjustment of the axial clearance and the pre-load of the bearing group supporting the rotating member. These issues limit the utilization of DSPO technology for the fluid machinery with a large capacity.